Russian liturgical music is not Byzantine chant. Yes, traditions like Znamenny can ultimately be traced back to Byzantine music, but along the way they evolved into something different. Later, Western polyphonic singing that had nothing to do with the Byzantine tradition was imported, and that informed the work of many prominent 19th-century and early 20th century Russian composers of sacred works.

That is why in the Orthodox Christian world, people perceive such a distinct difference between the liturgical singing of e.g. Greece, Albania, or Romania, and the singing of e.g. Ukraine or Russia.